1. Field of the Invention
The present invention relates to recording/reproducing apparatus and method preferable for application to a DVD reproducing apparatus and DVD recording/reproducing apparatus for carrying out recording and reproduction on an optical disc such as DVD-R, DVD-RW and the like.
2. Description of the Related Art
Conventionally, a write-once optical disc called compact disc-recordable (CD-R) has been widely prevailed as an optical disc capable of recording data. Wobbling grooves are formed in a data recording region of the CD-R such that they meander slightly depending on a wobbling signal indicating absolute position information or the like on a disc face. Data is recorded along this wobbling groove (the wobbling groove serves for a recording track).
When recording data in this recording track, a wobbling signal is detected from the wobbling groove so as to obtain absolute position information on the disc face, so that the data can be recorded at a target recording position appropriately.
Upon detecting the wobbling signal from the wobbling groove, reflected light of beam irradiated to the wobbling groove is received by a photo detector, whose entire light receiving region is divided to two parts with a dividing line optically parallel to a tangent line of the wobbling groove, and a differential of output from different light receiving regions is obtained and then, this differential signal is supplied to a band pass filter (BPF), in which a frequency (22.05 KHz) of a carrier of the wobbling signal is a central frequency. Consequently, the wobbling signal is detected form the wobbling groove.
When recording data in a recording track of the CD-R, a rotating operation of the CD-R is controlled so that the frequency of a wobbling signal extracted through the BPF turns to the predetermined frequency. Further, the wobbling signal extracted through the BPF is used as a reference signal for generating the recording clock signal.
The wobbling signal is continuous signal containing a frequency component synchronous with a rotation of the CD-R. Therefore, if a clock signal synchronous with the phase of this wobbling signal is generated with such wobbling signal as a reference signal, the clock signal used for recording accurately synchronous with a rotation of the CD-R can be generated.
In the meantime, improvement of recording capacity has been aggressively considered in the field of the write-once optical disc such as the CD-R. In recent years, development of digital versatile disc-recordable (DVD-R) has been accelerated as the write-once optical disc having a recording capacity about seven times that of the CD-R.
In the DVD-R, the pitch between adjacent recording tracks is substantially half that of the CD-R in order to increase the recording capacity aiming at intensifying the recording density. For the reason, when the wobbling signal is detected, a cross-talk is generated from right and left wobbling grooves located adjacent each other, so that the amplitude and phase of the wobbling signal may be fluctuated. Particularly, there occurs a problem that the wobbling signal in which the phase thereof is fluctuated by an influence of the cross-talk disables generation of a recording clock signal accurately synchronous with the rotation of the DVD-R.
As a method which solves such a problem and generates a recording clock signal accurately synchronous with the rotation of the DVD-R, according to Japanese Patent Application Laid-Open No. H10-293926, a difference in phase between the wobbling signal and a prepit signal from a prepit generated in land between adjacent grooves is detected and then, the difference in phase of the recording clock signal is adjusted based on this phase difference signal.
In the DVD-R, the prepit is generated in land between adjacent wobbling grooves corresponding to a prepit signal indicating absolute position information or the like on the disc face. By detecting the prepit signal from this prepit so as to obtain the absolute position information on the disc face, data can be recorded appropriately at a target recording position.
The prepit is recorded having a predetermined relation in phase with the wobbling signal and generated between adjacent lands such that the prepits do not overlap in the disc diameter direction. Therefore, the prepit signal detected from the prepit is not affected by the cross-talk.
According to technology disclosed in the aforementioned Japanese Patent Application Laid-Open No. H10-293926, by making effective use of the prepit signal when generating the recording clock signal, even if the wobbling signal is fluctuated in its time axis due to an influence of the cross-talk, the recording clock signal generated based on this wobbling signal is corrected appropriately. As a result, a recording clock signal accurately synchronous with the rotation of the DVD-R is obtained.
In the aforementioned DVD-R, when detecting the wobbling signal, the period of the wobbling signal is fluctuated by an influence of the prepit generated in a land adjacent the wobbling groove.
On the other hand, in the recording clock signal generating apparatus disclosed in Japanese Patent Application Laid-Open No. H10-293926, a BPF, which employs the frequency of a carrier of the wobbling signal as its central frequency, is used as a wobbling signal extracting means and a BPF output is binarized so as to extract the wobbling signal.
However, because in case of the DVD-R, the aforementioned prepit is generated such that it appears at every 16 periods of the wobbles in the wobbling groove and that further, the prepit appears on both sides of the wobbling groove, the period fluctuation of the binary signal produced by binarizing through the BPF is increased, so that an appropriate recording clock signal becomes difficult to generate.
Although a phase locked loop (PLL) circuit may be used for removing an influence by the prepit, if it is intended to remove the influence of the prepit using the PLL circuit, it is difficult to set up a range in which the PLL circuit is placed and further, the PLL circuit may make complicated the entire circuit structure of the recording clock signal generating apparatus.
The present invention has been achieved in views of the above-described problem and therefore, an object of the present invention is to provide recording/reproducing apparatus and method capable of obtaining an accurate recording/reproducing clock signal by removing an influence of the prepit upon the wobbling signal with a simple structure.
To achieve the above-described object, there is provided a recording and reproducing apparatus for recording and reproducing information in and from a disc-like recording medium including recording tracks each wobbled according to a predetermined frequency and information recording portions in which at least address information is recorded at a predetermined wobbling period interval, the recording and reproducing apparatus comprising: wobbling signal extracting means for extracting a wobbling signal from a reproduction output from the disc-like recording medium; reference clock generating means for generating a reference clock having a period shorter than the period of the wobbling signal; count means for binarizing the wobbling signal extracted by the wobbling signal extracting means to obtain a wobbling pulse and for counting and accumulating the number of pulses of the reference clock from the reference clock generating means for predetermined periods of the wobbling pulse to obtain a count value; dividing means for obtaining an average count value corresponding to an interval of an averaged period of the wobbling pulse by dividing the count value from the count means with the number of the predetermined periods; and wobbling pulse generating means for generating a wobbling pulse having a constant period as a recording and reproducing clock signal by dividing the reference clock based on the average count value.
According to a preferred embodiment of the present invention, at every second predetermined periods of the wobbing pulse, processing with the count means and the dividing means are carried out so as to update the average count value.
According to another preferred embodiment of the present invention, at the time of change-over from recording of information to reproduction and change-over from reproduction of information to recording, updating of the average count value is not carried out for a predetermined time.
According to still another preferred embodiment of the present invention, the count means starts accumulation and count of the reference clocks from a beginning of a wobbling pulse at a timing immediate before a wobbling pulse at a timing corresponding to a detection of the information recording portion.
According to other preferred embodiment of the present invention, the recording and reproducing apparatus further comprises a phase adjusting means for adjusting the phase of the generated wobbling pulse having the constant period with respect to a recording timing of information recorded in the information recording portion.
To achieve the above-described object, there is provided a recording apparatus for recording information in a disc-like recording medium including recording tracks each wobbled according to a predetermined frequency and information recording portions in which at least address information is recorded at a predetermined wobbling period interval, the recording apparatus comprising: wobbling signal extracting means for extracting a wobbling signal from a reproduction output from the disc-like recording medium; reference clock generating means for generating a reference clock having a period shorter than the period of the wobbling signal; count means for binarizing the wobbling signal extracted by the wobbling signal extracting means to obtain a wobbling pulse and for counting and accumulating the number of pulses of the reference clock from the reference clock generating means for predetermined periods of the wobbling pulse to obtain a count value; dividing means for obtaining an average count value corresponding to an interval of an averaged period of the wobbling pulse by dividing the count value from the count means with the number of the predetermined periods; and wobbling pulse generating means for generating a wobbling pulse having a constant period as a recording clock signal by dividing the reference clock based on the average count value.
To achieve the above-described object, there is provided a reproducing apparatus for reproducing information from a disc-like recording medium including recording tracks each wobbled according to a predetermined frequency and information recording portions in which at least address information is recorded at a predetermined wobbling period interval, the recording and reproducing apparatus comprising: wobbling signal extracting means for extracting a wobbling signal from a reproduction output from the disc-like recording medium; reference clock generating means for generating a reference clock having a period shorter than the period of the wobbling signal; count means for binarizing the wobbling signal extracted by the wobbling signal extracting means to obtain a wobbling pulse and for counting and accumulating the number of pulses of the reference clock from the reference clock generating means for predetermined periods of the wobbling pulse to obtain a count value; dividing means for obtaining an average count value corresponding to an interval of an averaged period of the wobbling pulse by dividing the count value from the count means with the number of the predetermined periods; and wobbling pulse generating means for generating a wobbling pulse having a constant period as a reproducing clock signal by dividing the reference clock based on the average count value.
To achieve the above-described object, there is provided a recording and reproducing method for recording and reproducing information in and from a disc-like recording medium including recording tracks each wobbled according to a predetermined frequency and information recording portions in which at least address information is recorded at a predetermined wobbling period interval, the method comprising the steps of: extracting a wobbling signal from a reproduction output from the disc-like recording medium; generating a reference clock having a period shorter than the period of the wobbling signal; binarizing the extracted wobbling signal to obtain a wobbling pulse; counting and accumulating the number of pulses of the reference clock for predetermined periods of the wobbling pulse to obtain a count value; obtaining an average count value corresponding to an interval of an averaged period of the wobbling pulse by dividing the count value with the number of the predetermined periods; and generating a wobbling pulse having a constant period as a recording and reproducing clock signal by dividing the reference clock based on the average count value.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.